1. Field of the Invention
This invention relates to machining a workpiece in an inert atmosphere. More specifically, the present invention relates to a process for machining a volatile metal workpiece in an inert atmosphere to reduce the occurrence of combustion of the resultant chips or fines and to reduce the waste material created by prior art volatile metal machining operations. In addition, the process may also include a vacuum system to remove the particulate matter; i.e., chips and fines resulting from the machining operation from the machining area.
2. Description of the Related Art
It is known in the art to machine volatile metals such as magnesium. However, the process is usually a "wet" process in which a coolant, typically a water soluble coolant, is used to cool the workpiece, lubricate the cutting equipment or tool, and flush the particulate matter; i.e., chips and fines from the machining area.
When machining a volatile metal such as magnesium, use of water-based coolant results in several problems: first, the magnesium reacts with the water to form hydrogen gas that besides being a fire hazard presents a serious particulate matter disposal and storage problem since the reaction continues; second, magnesium fines are flammable, presenting an additional hazard in that they may catch fire. A magnesium fire is extremely difficult to extinguish. One solution to insure that the particulates remain cool and stay below their ignition point is to use an oil-based coolant. Use of an oil-based coolant presents a fire hazard and creates a disposal problem as the particulate matter mixes with the coolant making it extremely difficult for recycling of both the coolant and the magnesium cuttings. Finally, any particulate matter produced during the machining operation may mix with the mist produced by the coolant and be carried into the atmosphere presenting a health hazard. While prior art exists for machining magnesium or other volatile metals, typically such a process is a slow machining process; i.e., it reduces the cutting speed to insure that the particulate matter remains cool, as opposed to high-speed machining which result in a "hot chip" which is subject to combustion. Further, while machining in an inert environment has been done on some exotic materials such as lithium on a limited production basis, such processes used low speed machining in laboratory environments and are not suitable for production machining operations.